In all honesty, I really think some dogs just have this. My dog is a mix breed, black and white nd also has red around her snout and mouth. Mostly it is where the white fur is. And her belly is a bit of a pink color. I think this is just natural pigmentation in their skin. If your pup isn't itching and the area doesn't look irritated and has been like this a long time, I'd just consider that one of her unique traits. :>)) When you say skin irritation? Is it irritated?